Ferromagnetic antenna systems



Jan. 20, 1959 w. J. POLYDOROFF 0,

FERROMAGNETIC ANTENNA SYSTEMS Filed March 26, 1956 7H ..s I 6 III" a'm'" United States Patent FERROMAGNETIC ANTENNA SYSTEMS Wladimir J.Polydorolf, Kensington, Md. Application March 26, 1956, Serial No.573,713

6 Claims. or. 343-787) This invention relates to ferromagnetic antennasystems, which generally comprised a pick-up coil associated with h. f.ferromagnetic material to increase the efliclency of such devices.

In the usual systems such as described in my U. S. Patents 2,266,262 and2,624,004 the pick-up coil is placed vertically, or with its axistowards the direction of propagation and a magnetic core in the field ofthe coil enhances the generation of electromagnetic effects in theantenna thus making it more efficient, and, as the second quoted patentshows, still more by elongating the core and the coil.

In my U. S. Patent 2,804,617, of which present invention is acontinuation in part, it has been shown that in addition to the abovedescribed effects the magnetic material actually attracts, deflects andconducts electromagnetic component of radiated field in a desireddirection and to a location where a coil may be installed. In thepreviously known systems the pick-up coil per se was used as a loopantenna with or without reinforcing action of the magnet so that itsrotation along the vertical axis produced well known figure eightpattern with its maxima and minima.

In the present invention the search coil is used with its planehorizontally or With its axis perpendicular to the direction ofpropagation, at which position the search coil is completely devoid ofits own pick-up of radiated energy. The energy is conducted to the coilby stationary or rotating ferromagnetic elements depending on whatpattern, omnidirectional or figure-eight, is desired to achieve. Itfollows that in the new system the antenna effect, due to direct pick-upof electrostatic component is entirely eliminated, as well as the staticdisturbanoes picked up by the coil as a vertical rod.

The principal object of the invention is to provide an antenna systememploying ferromagnetic means and a search coil placed with its axisvertically for vertically polarized waves in a permanent fixed positionthus dis pensing with commutating means for the coil and eliminatingelectrostatic pick-ups of the signal and static.

Another object is to avoid the troubles associated with atmosphericconditions, as the search coil and its cable may be completely sealed.

A further object is to provide a collector of electromagnetic radiationswhich produces an omnidirectional pattern without the disadvantages of avertical antenna which, as it is known, contributes greatly to thegeneration of static disturbances.

Those and other objects will be better understood if reference is madeto the accompanying drawing in which:

Fig. 1 shows a schematic representation of the invention.

Fig. 2 shows a modification of Fig. 1.

Fig. 3 shows a schematic presentation of another form.

Fig. 4 and Fig. 5 show detailed construction. of the invention.

Fig. 6 shows another variant of the construction.

a cylindrical piece 2 of high frequency ferromagnetic.

material, preferably of ferrite. Search coil 1 is connected through acable 13 with a transformer 3 whose secondary may be tuned to theincoming frequency by a capacitor 4. Thus far the described circuit ifproperly shielded is incapable of receiving any signal from an outsidesource. Two elongated rods 5 of a ferromagnetic material of highpermeability are now added as shown with their ends close to or incontact with the top and bottom ends of the cylinder 2. These rods nowpick up the radiated energy and transmit electromagnetic linesthroughout their length, into the cylinder and through the bottom rod.The search coil now picks up the energy and transmits it in the form ofcurrent to the receiving system.

When rods are simultaneously rotated in the horizontal plane it isestablished that the maximum pick-up occurs when their direction isperpendicular to theemitter and very sharp minimum in excess of 20 db isobserved when the rods are in line with the emitter. Thus a directionalantenna system is produced without rotation of the coil producing aconventional figure eight pattern by simple mechanical rotation ofplurality of magnetic elements.

In Fig. 2 the pair of rotating elements may be placed not in line but atan angle, as before, one at the top and the other at the bottom ofcylinder 2 in which case if both rods are simultaneously rotated asimilar pattern is obtained, the maxima and minima corresponding to thedirection of bisector of the angle between two rods.

When two or more rods are placed on top and the bottom of cylinder 2 inthe diametrically opposed manner, the antenna shown on Fig. 3 exhibits asomewhat reduced pick-up completely devoid of direction properties,similar to the pattern obtainable by a vertical rod antenna, except thatthe pick-up is due solely to the electromagnetic component of the wave.The vertical antenna has been used in directional finding systems todetermine the sense of the signal and has been found to be the source ofelectrostatic disturbances. By proper phasing of the signal obtainablefrom the antenna of Fig. 3 and combining same with the "figure eightpattern of above described directional antennas one can obtain a signalfor sense determination.

Referring now. to Fig. 4 and Fig. 5 one can see the actual constructionof one embodiment of directional antenna. A ferrite spool 2 issurrounded by the coil 1 which is moulded in a plastic container 6 withflanges 7 and supports 8 throughwhich flanges and supports theconnections are made to the cable 13. The ferromagnetic spool 2 andtworods 5 are assembled together on shaft 9 which rotates in the bearinglllof mounting plate 11. rounded ends and a taper to a greater width atthe outer ends for greater pick-up of energy.

The construction of Fig. 6 is somewhat difierent from that of previousfigure in that the search coil 1 and its ferromagnetic spool 2 arepermanently fixed on the tubular bearing 10 and the shaft 9 terminateson top with two brackets 12 to which bracketsthe ferromagnetic rods 5are attached. The inner ends of rods 5 are shaped to conformwith thecylindrical surface of the spool 2 and adjusted to form a small circulargap between the spool and the rods. In addition, the lower 'revolvingend may be Z-shaped so as to have both rods As Fig. 5 shows the rods 5may have V iead-in wires from the coil may be brought out within thebearing 10 and terminated by a cable 13.

As can be seen from the description the search coil is placedhorizontally for vertically polarized wave, so that direct pick-up ofelectromagnetic component is-elirninated and its axial length is verysmall so that antenna efiect is negligible even without screening. Thecoil, being in a fixed position, can be easily treated against moistureand the commutating means are entirely eliminated.

Having thus described my invention, what I claim is:

1. A directional antenna system for the reception of electromagneticradiations having a ferromagnetic core of high permeability in the formof a hollow body of rotation, the axis of said core being in thedirection of polarization of said radiations, a search coil around saidcore, a pair of elongated ferromagnetic bars, each being in the planeperpendicular to said axis, said pair being connected together forrotation by a common shaft protruding through the hollow of said core,the respective inner ends of said elongated oars being connected throughthe smallest possible airgap to the opposite end portions of said core.

2. A directional antenna system according to claim 1, characterized inthat said ferromagnetic bars have rectangular cross-sections.

3. A directional antenna system according to claim 2, characterizedinthat-said cross-sectionsare increasing towards the outer ends of saidbars.

4. A directional antenna system according to claim 1, characterized inthat said search coil has self-supporting means independent of saidrotation.

5. A directional antenna system according to claim 4, characterized inthat said supporting means contain connecting leads to said coil.

6. A directional antenna system according to claim 1, characterized inthat said ferromagnetic core and said bars are made of high permeabilityferrite.

References Cited inthe file of this patent UNITED STATES PATENTS2,624,004 Polydoroff Dec. 30, 1952 2,718,003 Hemphill Sept. 13, 19552,740,113 Hemphill Mar. 27, 1956 2,755,468 Mountjoy July 17, 1956FOREIGN PATENTS 735,429 Germany May 14, 1943

